If we measured their depression with a test that doctors use, before and after working their way through the book (which
takes 30 days) would we see a difference?

The test we used, called the PHQ-9 – the 9-item Patient Health Questionnaire) – produces a score between 0 and 27, with 0 meaning no depression, and 27 representing the most severe depression possible.

The score range is divided into five bands that, apart from the highest division, are drawn at five-point intervals.

Healthcare professionals use the PHQ-9 to help decide, in part, what treatment – such as antidepressants or psychotherapy / counselling might best help a patient.

They also ask patients to complete the test as one way of determining whether or not a chosen treatment is working.

When the PHQ-9 is used to measure progress, the rule of thumb is that a reduction in score of 5 points or more over a period of 4-6 weeks means the current treatment regime is working, and should therefore be continued.

We asked 51 people to use the book for 30 days, completing the PHQ-9 before they started, and again when they’d finished.

The participants were a randomly chosen subset of readers of the Moodnudges blog who weren’t pre-selected on the basis of being depressed, so the sample included a range of individuals from those who had only the most minimal depression to others who were experiencing moderately severe depression.

The results, which can be seen in graph form, show two important findings:1. Across the board, the average reduction in PHQ-9 score over 30 days was 5.3, suggesting that using Nudge Your Way to Happiness can be as clinically effective as antidepressants or psychotherapy.

2. The greatest reductions in score were seen in those who were most depressed to start with. On average these participants’ scores fell from a level definitely placing them in the Moderately Severe category to one at the very lowest end of the Moderate division: only a whisker away from being labelled Mild.

Future work could involve working with a larger sample, and structuring the study as a randomized controlled trial. But these early results do seem promising.